Sister-chromatid exchanges and cytotoxicity in cultured Indian muntjac cells treated with alkylating agents.

6 monofunctional alkylating mutagens/carcinogens -- 4 N-nitroso and 2 methanesulfonate compounds -- differed in their efficiency for inducing sister-chromatid exchanges (SCEs) when normalized on cytotoxicity. SCE induction occurred only at highly cytotoxic doses. Ethylating agents were, on a molar basis, generally less potent inducers of SCEs, and they were also less cytotoxic than the corresponding methylating agents. The observed differential action spectrum of the 6 alkylating agents is discussed in the light of recent ideas on the interaction between alkylating mutagens with DNA and the role of specific DNA lesions in the formation of SCEs.